The invention relates to an externally ignited, four-cycle, piston-type internal combustion engine. Engines of this type are also known as Otto engines.
In a known internal combustion engine of this type (German Democratic Republic Patent No. 91,936), a cylindrical depression is disposed in the center of the piston, coaxial with its longitudinal axis, and openings directed diagonally downward from the piston top lead into this depression, the openings being inclined in such a manner that the gas jets flowing through them into the depression, toward the end of the compression stroke are intended to generate in the depression a vortex flow running approximately parallel to the piston top. The high flow losses of the gas or mixture flows which pass through the openings are disadvantageous. Furthermore, toward the end of the compression stroke, the mixture also flows in substantial quantities axially and radially into the depression approximately radially from all sides and this action hinders the formation of an effective vortex flow in the depression. It is not possible to attain high compressions of the mixture. Combustion also takes place relatively slowly in such an engine, with the result that a substantial quantity, in percentage terms, of harmful, partially combusted components is emitted.